How has Macbeth "murdered Sleep?"No
This line is a grim foreshadowing of what is to come, as Macbeth himself seems to fear. He goes on to say that the voice he heard said that "Macbeth shall sleep no more." This proves to be true. Not only has Macbeth murdered Duncan in his sleep, but he has saddled himself and his wife with a psychological burden, guilt, that will rob them both of the ability to sleep at night. Very soon after the murder, Macbeth feels pangs of guilt that not only keep him up at night, but cause him to see apparitions, like that of Banquo. After the murder of his friend, however, he really shows no signs of guilt, becoming a monster devoid of conscience. At this point, his wife is consumed by guilt, and it is precisely in her sleep where this guilt manifests itself. In one of the most famous scenes in the play, she sleepwalks, attempting in vain to scrub imaginary spots of blood from her hands. Her complicity in the assassination of Duncan has murdered her sleep as well.
By killing Duncan in his sleep, Macbeth has brought tremendous guilt on himself and imagines he hears a voice saying "Macbeth has murdered sleep!" He feels he will never sleep again because he destroyed the slumber (and life) of Duncan. Ironically enough, his wife's sleep is also destroyed by guilt as we see later when she is sleep walking.
Methought I heard a voice cry 'Sleep no more!
Macbeth does murder sleep', the innocent sleep,
Sleep that knits up the ravell'd sleeve of care,
The death of each day's life, sore labour's bath,
Balm of hurt minds,... (2.2)
One who can not sleep typically harbors a busy mind or a guilty conscience or a combo of the two. Those who are innocent are able to slumber peacefully. Macbeth has murdered sleep for himself and also for his wife (who later sleepwalks as a result of her guilt) because he takes the innocent life of Duncan who trusts Macbeth both as his loyal countryman and as his host. Macbeth has broken many rules by taking Duncan's life, and he will never be able to sleep peacefully again as a result of it: "'Sleep no more!/Macbeth does murder sleep'...."